Inflammatory airway disease (IAD) in horses, which has been historically difficult to diagnose, might soon be easily detected via a simple blood test, according to a French equine respiratory specialist.

"The results of our present study indicate that IAD is associated with a detectable, albeit moderate, increase in circulating rates of surfactant protein D (SP-D) in the blood," said Eric Richard, DVM, MSc, PhD, researcher at the Frank Duncombe Laboratory in France, at the 2012 French Equine Research Day held March 1 in Paris. Richard relayed that SP-D plays a principle role in immunity in the alveoli–the thousands of small balloonlike structures within the lungs that participate in the exchange of gases used in breathing.

Inflammatory airway disease can cause poor performance and exercise intolerance in horses, and it is occasionally associated with a slight cough at rest, said Richard. As it is generally not an infectious disease, laboratory testing of blood samples cannot provide clear links to the condition. The most effective evaluation method currently available is an examination of the cells of the lungs using a bronchoalveolar lavage (BAL), an invasive and expensive procedure requiring sedation, Richard noted.

In his preliminary study, Richard and his colleagues tested the blood serum of 20 healthy horses and 22 horses previously diagnosed with IAD, before and after 60 minutes of treadmill exercise. The IAD horses had significantly higher amounts of SP-D in the blood compared to the healthy horses, both before and after exercise. However, there was no significant difference in the amount of SP-D before and after exercise within each of the two groups. In other words, exercise did not seem to affect the amount of circulating SP-D, whether in healthy horses or those with IAD